🔍 Key Concepts

• Specific gravity as a ratio (no units) • How a hydrometer works by floating higher/lower depending on liquid density • The role of water as a reference liquid in many marine measurements

💭 Think About

• Which choice describes a comparison of two densities (or weights per unit volume), not just masses or weights? • In specific gravity, is the comparison between the same substance in two different conditions, or between the substance and a reference liquid? • Think about what liquid a hydrometer is usually calibrated against for marine use—what does it normally compare the test liquid to?

✅ Before You Answer

• Identify which option clearly refers to a ratio between the test liquid and water. • Eliminate any option that talks only about mass without reference to volume or density. • Check that the option you’re leaning toward reflects that specific gravity is dimensionless (no units), meaning it’s a pure comparison, not an absolute measurement.